This invention relates generally to fasteners such as are used for securing two or more sheets of sheet metal paneling for outdoor storage structures such as silos or the like. More particularly, the invention relates to the type of fastener having a plastic cap or the like secured to the head of the fastener which may be colored to match the metal paneling to blend in with the paneling and is protected against corrosion by the plastic cap. Most importantly, this invention relates to a fastener consisting of a bolt and nut in which the fastener is specifically designed not to be driven but merely to be held against rotation during tightening of the nut. The cap not only protects the bolt from corrosion, but the seals resulting from use of this fastener normally are hermetic as well as water tight.
There has been and still is great need in industry to provide a capped fastener, that is fastener having a plastic cap or covering to prevent corrosion of the fastener and also to provide a water tight or hermetic seal when the fastener is in place. This is particularly critical in outdoor construction of storage facilities such as silos, barns and the like. Heretofore, there has not been commercially available a fastener which successfully employs a plastic cap, there being relatively few commercially available and there being none which is generally satisfactory. All of the commercially available fasteners suffer from the problem of the plastic cap being stripped from the screw during driving.
Further, the plastic underneath the screw head splays outwardly from underneath the head as the screw is tightened, thereby losing the most important sealing qualities of the plastic cap.
The patent literature shows several variations of capped fasteners, all of which are the driving type, none being directed to combination fasteners of bolts and nuts. U.S. Pat. No. 4,154,138 issued May 15, 1979 to Malone describes a screw with a plastic head showing a driving screw having a multifaceted head to ensure that the plastic cap remains on the screw during driving.
U.S. Pat. No. 3,385,492 issued May 27, 1975 to Gutshall describes a driving fastener having a plastic cap on the head thereof in which a flexible and yieldable center portion permits the insertion of a driving tool into a tool receiving recess in the screw head.
U.S. Pat. No. 3,693,495 issued Sept. 26, 1972 to Wagner shows a driving screw having a plastic head and washer portion in which the screw head is multifaceted in order to retain the plastic cap thereon during driving.
U.S. Pat. No. 3,639,137 issued Feb. 1, 1972 to Marinelli describes a rivot having pressure rupturable capsules on the shank thereof, the capsules containing liquid sealant.
U.S. Pat. No. 3,557,654 issued Jan. 26, 1971 to Weidner describes a composite fastener having a plastic head with a thin elastic skirt for forming liquid seals when the fastener is driven.
U.S. Pat. No. 3,134,290 issued May 26, 1964 to Jentoft describes a fastener having a plastic cap with a flexible lip and a conical elastic and flexible skirt forming liquid seals when the fastener is driven.
U.S. Pat. No. 2,032,099 issued Feb. 25, 1936 to Rosenberg shows a fastener having a soft metal head or cap which acts as a washer for the fastener.